Conventionally, polyimide resins and polybenzoxazole resins, which are excellent in heat resistance, electric insulation, and the like, have widely been used for a surface protection film or interlayer insulating film in a semiconductor device, an insulating layer in an organic electrolytic device, and/or a flattening film in a TFT substrate. Furthermore, photosensitive polyimides and photosensitive polybenzoxazoles to which photosensitive properties have been provided have been studied to enhance the overall productivity. However, those resins in the film form are well dissolved during development or much influenced by an environment in which they are used, and thus it has been indicated that they are difficult to use in industry.
On the one hand, a positive photosensitive resin composition containing a hydroxystyrene resin, a polyamic acid, and a quinonediazide compound has been proposed (Patent Literature 1). In this resin composition, the solubility in an alkaline solution, which is a developer solution, is reduced in an unexposed portion based on the interaction between the phenolic hydroxyl group of the hydroxystyrene resin and the quinonediazide compound. Consequently, the solubility in the alkaline solution is significantly increased in an exposed portion through the light-induced acid generation by the quinonediazide compound. This difference in the solubility in the alkaline solution between the unexposed portion and the exposed portion allows the production of a positive relief pattern.
Furthermore, a positive photosensitive resin composition containing a polyhydroxystyrene resin and alkoxymethyl group or methylol group has been proposed, which achieves an increased sensitivity and a lowered stress (Patent Literature 2).
On the other hand, a method of reducing the stress generated during the production of a cured film and thereby achieving a lower warpage has been proposed, in which a flexible alkyl group, alkylene-glycol group, and/or siloxane bond is introduced into the repeating unit of an alkali-soluble cyclized polyimide or polybenzoxazole (Patent Literature 3).